Hollow magnesium oxide composite having cavity and manufacturing method therefor

Abstract

The present invention relates to a hollow magnesium oxide composite having a cavity and a manufacturing method therefor, the hollow magnesium oxide composite comprising: a core portion having a hollow; and a shell portion comprising magnesium oxide crystal grains and a metal element different from magnesium and having at least one cavity communicating with the hollow.

Description

Hollow magnesium oxide composite having a cavity and method for manufacturing the same

[0001] The present invention relates to a hollow magnesium oxide composite having a cavity and a method for manufacturing the same.

[0002] Electronic devices consist of electronic components such as laminates, printed circuit boards, and multilayer circuit boards. Recent electronic devices are equipped with high-capacity power components and manufactured with high-density internal configurations for miniaturization, requiring a higher level of heat dissipation and weight reduction compared to conventional devices. Silica and alumina have been primarily used as fillers in resin compositions for conventional semiconductor encapsulation. However, due to its low thermal conductivity, silica lacks sufficient heat dissipation capacity to handle the increased heat generation resulting from high integration, high power consumption, and high speeds, which poses a problem for the stable operation of semiconductors. On the other hand, while alumina, which has higher thermal conductivity than silica, offers improved heat dissipation, its high density and excessive hardness lead to severe wear on mixing machines, molding machines, and molds.

[0003] Accordingly, magnesium oxide, which possesses higher thermal conductivity and a relatively lower density compared to alumina, is being considered as a material for semiconductor encapsulation resin fillers. However, magnesium oxide powder has a problem in that it cannot maintain stable physical properties due to its higher hygroscopicity compared to alumina powder. Specifically, when magnesium oxide powder is used as a semiconductor encapsulation resin filler, the magnesium oxide reacts with moisture in the air to form magnesium hydroxide on its surface, causing the volume of the filler to expand. This leads to problems such as crack formation and a decrease in thermal conductivity.

[0004] Therefore, for the use of magnesium oxide as a heat dissipation filler, research is needed on lightweight magnesium oxide with improved heat dissipation performance and long-term durability.

[0005] [Prior Art Literature]

[0006] [Patent Literature]

[0007] Republic of Korea Registered Patent Publication No. 10-1878963

[0008] The present invention aims to provide a hollow magnesium oxide composite having a cavity with improved moisture resistance and reduced weight, and a method for manufacturing the same.

[0009] However, the technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0010] One embodiment of the present invention provides a hollow magnesium oxide composite having a cavity, comprising: a core portion having a hollow cavity; and a shell portion having at least one cavity communicating with the hollow cavity, comprising magnesium oxide crystal grains and a metal element different from magnesium.

[0011] Another embodiment of the present invention provides a method for manufacturing a hollow magnesium oxide composite having a cavity, comprising: a slurry preparation step of mixing a magnesium oxide precursor comprising at least one of Mg(OH)2 powder and MgO powder, an inorganic additive, a thickener, a dispersant, and water to form a slurry; a spray drying step of preparing the slurry into granular powder using a spray drying method; and a sintering step of crystallizing the granular powder by sintering treatment.

[0012] Another embodiment of the present invention provides an organic-inorganic composite in which particles composed of a hollow magnesium oxide composite having the cavity are dispersed within a polymer matrix.

[0013] The hollow magnesium oxide composite having a cavity according to the present invention exhibits excellent moisture resistance, thereby resolving problems such as the degradation of physical properties caused by the low moisture resistance of conventional magnesium oxide. Furthermore, when the hollow magnesium oxide composite having a cavity according to the present invention is applied to products such as heat dissipation films, the presence of the cavity allows for the filling of polymer materials into the hollow space, thereby providing the advantage of high durability along with product weight reduction.

[0014] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by a person skilled in the art from the description below.

[0015] Figure 1 shows images after spray drying and sintering in the formation of hollow particles having cavities.

[0016] Figure 2 shows an example for determining the degree of internal filling of a particle when a hollow particle having a cavity is impregnated with epoxy resin.

[0017] Figures 3 to 10 are SEM images showing sintered particles prepared according to Examples 1 to 8, respectively.

[0018] Figures 11a and 11b are SEM images showing a sintered particle prepared according to Comparative Example 1 and a cross-section thereof, respectively.

[0019] Figures 12 and 13 are SEM images showing sintered particles prepared according to Comparative Example 2 and Reference Example 1, respectively.

[0020] Figure 14 shows the XRD analysis results before and after a 72-hour test at 85°C and 85%RH of sintered particles prepared according to Example 5.

[0021] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description.

[0022] However, this is not intended to limit the present invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention. In describing the present invention, detailed descriptions of related prior art are omitted if it is determined that such detailed descriptions may obscure the essence of the present invention.

[0023] The terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0024] In this specification, when a part is described as "comprising" a certain component, it means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0025] In this specification, when a member is described as being located "on" another member, this includes not only cases where a member is in contact with another member, but also cases where another member exists between the two members.

[0026] The present invention will be described in detail below.

[0027] One embodiment of the present invention provides a hollow magnesium oxide composite having a cavity, comprising: a core portion having a hollow cavity; and a shell portion having at least one cavity communicating with the hollow cavity, comprising magnesium oxide crystal grains and a metal element different from magnesium.

[0028] The shell portion of the hollow magnesium oxide composite having a cavity according to the present invention is a layer with a dense structure that allows the hollow of the core portion to be formed, and furthermore, has a structure in which the external and internal hollows can communicate due to the presence of the cavity. Specifically, the shell portion is formed by densely contacting magnesium oxide crystal grains, and even during the growth of the crystal grains constituting the shell portion, the opening regions between the crystal grains are maintained so that a cavity can be provided. Due to the presence of the cavity, the hollow magnesium oxide composite having a cavity can be filled with another material inside; this allows the polymer material to be filled into the internal hollow when manufacturing a heat dissipation product using a polymer material, thereby increasing the durability of the product and enabling weight reduction.

[0029] Furthermore, the shell portion further comprises a metal element different from magnesium in the magnesium oxide-based base material, and due to the presence of said metal element, the formation of magnesium hydroxide on the surface of the magnesium oxide due to the absorption of moisture from the air can be significantly reduced or prevented. Through this, the hollow magnesium oxide composite having said cavity can solve the problem of changes in physical properties caused by moisture absorption in general magnesium oxide. In addition, the hollow magnesium oxide composite having said cavity can also have the advantage of lowering manufacturing costs by lowering the sintering temperature during manufacturing due to said metal element.

[0030] According to one embodiment of the present invention, the metal element may include at least one selected from the group consisting of Ti, Nb, Zr, Ga, B, Fe, Sn, Mn, Si, V, Ta, Sb, Y, Eu, Er, Al, and Yb. Specifically, the metal element may include at least one selected from the group consisting of Ti, Nb, Yb, and V.

[0031] The shell portion of the hollow magnesium oxide composite having a cavity according to the present invention may be a sintered body having magnesium oxide containing the metal element as a base material, or a ceramic having magnesium oxide as a base material. Additionally, the shell portion of the hollow magnesium oxide composite having a cavity according to the present invention may be a solid solution containing the metal element within the magnesium oxide crystal structure. As described above, the cavity in the shell portion may be an area where the sintered body constituting the shell portion does not exist, and this may be partitioned as an empty area where the magnesium oxide crystal grains do not come into contact with each other. According to one embodiment of the present invention, the cavity may be provided surrounded by the magnesium oxide crystal grains of the shell portion.

[0032] According to one embodiment of the present invention, the metal element may be provided by substituting it at the position of the magnesium element of the magnesium oxide crystal grain. More specifically, the metal element is Mg of the unit cell of the magnesium oxide crystal grain. 2+ At least a portion of it may be provided by being substituted with the above metal element.

[0033] According to one embodiment of the present invention, the metal element may be provided in the form of an oxide on the surface of the magnesium oxide grain. Specifically, the metal element may be provided in the form of an oxide on the interface and / or surface of the magnesium oxide grain. More specifically, the metal oxide may exist as another phase at the magnesium oxide grain boundary. In this case, the metal oxide may be irregularly present on the surface of the shell portion of the hollow magnesium oxide composite having the cavity.

[0034] According to one embodiment of the present invention, the metal element may be provided by substituting it at the magnesium element position of the magnesium oxide crystal grain, and at the same time, may be provided in the form of a metal oxide on the surface of the magnesium oxide crystal grain.

[0035] According to one embodiment of the present invention, the content of the metal element may be 0.02 at.% or more and 6 at.% or less with respect to the magnesium element (with respect to 100 at.% of the Mg element). Specifically, the content of the metal element may be 0.02 at.% or more and 5 at.% or less, 0.02 at.% or more and 4 at.% or less, 0.02 at.% or more and 3 at.% or less, 0.02 at.% or more and 2 at.% or less, 0.04 at.% or more and 2 at.% or less, 0.04 at.% or more and 0.4 at.% or less, 0.1 at.% or more and 2 at.% or less, 0.09 at.% or more and 0.5 at.% or less, or 0.1 at.% or more and 0.4 at.% or less with respect to the magnesium element. When the content of the metal element is within the above range, the moisture resistance of the hollow magnesium oxide composite having the cavity can be significantly improved, and furthermore, the sintering temperature during manufacturing can be lowered. In addition, if the content of the metal element is below the above range, the effect of improving the moisture resistance of the hollow magnesium oxide composite having the cavity may not be sufficient, and if the content of the metal element exceeds the above range, the metal element or metal oxide may interfere with the formation of crystal grains in the shell portion of the hollow magnesium oxide composite having the cavity.

[0036] The content of the above metal element can be determined by methods known in the industry, for example, through EDS, WDS, EPMA, XRF, or Rietveld refinement of neutron and X-ray diffraction, and can also be determined through ICP analysis.

[0037] According to one embodiment of the present invention, the hollow magnesium oxide composite having the cavity may be a spherical particle. The spherical shape refers to a shape that can be confirmed as spherical through SEM images, etc., and does not mean a shape with 100% sphericity. For example, the hollow magnesium oxide composite having the cavity may be a spherical particle with a sphericity of 60% or more.

[0038] According to one embodiment of the present invention, the hollow may be composed of 1 to 20 spherical pores. Specifically, the hollow may be formed as a single pore having the same shape as the composite particle (e.g., spherical). Alternatively, the hollow may be provided in a form in which a plurality of pores overlap or are spaced apart from each other.

[0039] According to one embodiment of the present invention, the particle size of the hollow magnesium oxide composite having the cavity may be 10 μm to 300 μm. Specifically, the particle size of the hollow magnesium oxide composite having the cavity may be 10 μm to 250 μm, 10 μm to 200 μm, or 10 μm to 150 μm. The particle size may refer to the average particle size of the particles.

[0040] According to one embodiment of the present invention, the diameter of the cavity may be 0.01 to 0.7 times the diameter of the composite particle. Specifically, the diameter of the cavity may be 0.05 to 0.5 times the diameter of the composite particle.

[0041] According to one embodiment of the present invention, the thickness of the shell portion of the hollow magnesium oxide composite having the cavity may be 1 μm to 40 μm. Specifically, the thickness of the shell portion of the hollow magnesium oxide may be 1 μm to 30 μm, or 2 μm to 20 μm. The shell thickness may refer to the average thickness. The hollow magnesium oxide composite having the cavity has the advantage of being lighter by having the aforementioned particle size and shell thickness.

[0042] According to one embodiment of the present invention, the content of magnesium oxide crystal grains in the shell portion of the hollow magnesium oxide composite may be at least 90 wt% with respect to the total composite. Specifically, the content of magnesium oxide crystal grains may be at least 92 wt% or 95 wt% with respect to the total composite.

[0043] According to one embodiment of the present invention, the hollow magnesium oxide composite having the cavity may have a weight gain rate of less than 1% after a moisture resistance test for 72 hours under an atmosphere of 85°C and 85%RH. Specifically, the hollow magnesium oxide composite having the cavity may have a weight gain rate of less than 0.7% or 0.5% or less after a moisture resistance test for 72 hours under an atmosphere of 85°C and 85%RH. The weight gain rate of conventional magnesium oxide in the moisture resistance test results was generally over 10%, and even when the sintering temperature was increased, the weight gain rate exceeded 1%. In contrast, the hollow magnesium oxide composite having the cavity according to the present invention exhibits significantly improved moisture resistance results compared to conventional magnesium oxide.

[0044] Another embodiment of the present invention provides a method for manufacturing a hollow magnesium oxide composite having a cavity. Specifically, another embodiment of the present invention provides a method for manufacturing a hollow magnesium oxide composite having a cavity, comprising: a slurry preparation step of mixing a magnesium oxide precursor comprising at least one of Mg(OH)2 powder and MgO powder, an inorganic additive, a thickener, a dispersant, and water to form a slurry; a spray drying step of preparing the slurry into granular powder using a spray drying method; and a sintering step of crystallizing the granular powder by sintering treatment.

[0045] Slurry manufacturing stage

[0046] The above slurry preparation step may involve preparing a mixture by mixing a magnesium oxide precursor containing at least one of Mg(OH)2 powder and MgO powder, an inorganic additive, a thickener, a dispersant, and water, and then slurrying the mixture. Additionally, the mixture may further include a dispersion stabilizer.

[0047] In the above slurry preparation step, Mg(OH)2 powder and / or MgO powder may be used as a precursor for magnesium oxide. When MgO is used as a precursor for magnesium oxide, since it reacts with water (H2O) as a solvent and is entirely converted into Mg(OH)2, using MgO powder as a precursor in an aqueous system can be substantially the same as using Mg(OH)2 powder.

[0048] Water is used as the solvent in the above slurry preparation step. Specifically, the water may be distilled water or deionized water. The use of water in the above slurry preparation step has the advantage of facilitating the formation of spherical granules during the spray drying step due to its high surface tension. Furthermore, conventional technology for manufacturing while maintaining the MgO powder state requires the use of organic solvents to maintain the MgO powder state within the slurry, which leads to problems such as volatilization and toxicity of the organic solvents. In contrast, since the present invention uses water as the solvent, the magnesium oxide precursor exists in the aqueous system in the form of Mg(OH)2 powder without dissociating significantly, which has the advantage of being stable and having high safety.

[0049] In order to manufacture a hollow magnesium oxide composite having a cavity according to the present invention, it is necessary to form hollow granular particles having a cavity through spray drying and then crystallize them by sintering. That is, in order to form hollow granular particles having a cavity through spray drying, it is necessary for the magnesium oxide precursor (i.e., Mg(OH)2) to be stably dispersed in the form of particles within the slurry. Therefore, the mixture in the slurry preparation step may further include a dispersant, and specifically, may include a dispersant and a dispersion stabilizer. Furthermore, when the slurry is mechanically ground before spray drying, it is necessary to prevent the magnesium oxide precursor (i.e., Mg(OH)2) from being finely pulverized and the degree of dissociation from increasing; at this time, the dispersant, more specifically the dispersant and the dispersion stabilizer, can prevent the dissociation of the magnesium oxide precursor in the solvent and ensure that it is evenly dispersed in the form of particles.

[0050] According to one embodiment of the present invention, the dispersant may be an aqueous dispersant. Specifically, the dispersant may be a carboxylate-based dispersant. Specifically, the dispersant may be an ammonium polycarboxylate-based dispersant.

[0051] According to one embodiment of the present invention, the dispersion stabilizer can stabilize the viscosity of the slurry by preventing the dissociation of Mg(OH)2 particles within the slurry of the dispersant, and / or by enhancing the dispersion effect of Mg(OH)2 particles caused by the dispersant. For example, if the dispersant is a polycarboxylate ammonium salt-based dispersant, the dispersion stabilizer may be ammonium hydroxide. Specifically, if the dispersant is a polycarboxylate ammonium salt-based dispersant, it dissolves in water to form carboxylate anions and ammonium cations [R-COOH . NH3↔ R-COO - + NH4 + (in aqueous)]. Ammonium cations promote the dissociation of Mg(OH)2 and [Mg(OH)2(s) + NH4 + (aq) ↔ Mg 2+ (aq) + 2NH4OH(aq)], the carboxylate anion lacks stability against Mg₂ cations and reacts with cations dissociated from the slurry precursor to form an insoluble salt [Mg 2+ + R-COO - → (R-COO)2Mg] exists in the form of a precipitate, which poses a problem by hindering the dispersibility of Mg(OH)2 particles. To minimize the above problem, ammonium hydroxide is added as a dispersion stabilizer, Mg(OH)2(s) + 2NH4 + (aq) ↔ Mg 2 By inducing a reverse reaction in the (aq) + 2NH4OH(aq) reaction, Mg(OH)2 particles can be stably present in the aqueous slurry, thereby suppressing the generation of Mg2 cations. Therefore, in the case of polycarboxylate-based dispersants, a problem may arise where they cannot perform their role as dispersants because they combine with ions in the aqueous system to form precipitates; thus, the mixture in the slurry preparation step may further include a dispersion stabilizer.

[0052] According to one embodiment of the present invention, the slurry manufacturing step may further include a step of mechanically grinding the mixture. The mechanical grinding may utilize a ball mill, bead mill, hammer mill, roll crusher, jet mill, or finish mill, but is not limited thereto, and any mechanical grinding method performed in the slurry manufacturing process is applicable.

[0053] According to one embodiment of the present invention, the slurry preparation step may involve mechanically grinding the mixture and then adding the dispersion stabilizer. Alternatively, the slurry preparation step may involve mechanically grinding the mixture and adding the dispersion stabilizer. When the mixture is mechanically ground and slurried, a precipitate may be formed due to a reaction with ions derived from the dispersant; therefore, the dispersion stabilizer may be added to prevent this.

[0054] The inorganic additive in the above-described slurry preparation step is intended to provide a metal element included in the shell portion of the hollow magnesium oxide composite having the aforementioned cavity, and may be substituted into the crystal structure of the magnesium oxide crystal grains through the sintering step to form a solid solution, or may form a metal oxide provided on the magnesium oxide crystal grains. The inorganic additive can significantly reduce the reactivity of the hollow magnesium oxide composite having the cavity with moisture or substantially eliminate reactivity with moisture to provide moisture resistance, and can also ensure economic efficiency by lowering the sintering temperature during the sintering step.

[0055] According to one embodiment of the present invention, the inorganic additive may be selected from the group consisting of oxides, hydroxides, or carbonates comprising at least one selected from the group consisting of Ti, Nb, Zr, Ga, B, Fe, Sn, Mn, Si, V, Ta, Sb, Y, Eu, Er, Al, and Yb. Specifically, the inorganic additive may be an oxide of a metal selected from the group consisting of Ti, Nb, Zr, Ga, B, Fe, Sn, Mn, Si, V, Ta, Sb, Y, Eu, Er, Al, and Yb, or a combination of two or more metal oxides. More specifically, the inorganic additive may comprise at least one metal oxide selected from the group consisting of TiO2, Nb2O5, ZrO2, Ga2O3, Mn2O3, B2O3, Fe2O3, SnO2, MnO2, SiO2, V2O3, V2O5, Ta2O5, Sb2O5, Y2O3, Eu2O3, Er2O3, Al2O3, YbO, and Yb2O3.

[0056] The above-mentioned thickener, through the above-mentioned manufacturing method, enables the internal hollow of a hollow magnesium oxide composite having a cavity to be formed more effectively, and simultaneously allows the cavity in the shell portion to be formed. Specifically, the above-mentioned thickener is dissolved in water, which is a solvent, to increase the viscosity of the slurry. This facilitates the formation of a shell by rapidly forming a film on the outer surface during high-temperature drying after the formation of slurry droplets during the spray drying step. The shell hinders the evaporation of internal moisture, and the vaporized moisture remaining inside may exist at high pressure within the particle. At this time, the moisture vaporized at high pressure may cause the shell to swell or penetrate the relatively thin film portion to form a cavity on the shell surface. The cavity formed in this manner can be maintained as a cavity in the shell portion of the sintered particle through a subsequent sintering step. That is, the thickener that controls the physical properties of the above slurry can act as a binder during spray drying to create a hard and blocked surface layer on the granule surface or effectively form a film, thereby playing a role in controlling the formation of hollows in the particles and cavities in the shell portion.

[0057] FIG. 1 shows images after spray drying and sintering in the formation of hollow particles having cavities. As described above, a slurry containing a thickener according to the present invention can be formed into granular particles having a shell with an internal hollow and cavity through a spray drying step. Then, the granular particles can be sintered to form a shell portion having a cavity surrounded by crystal grains.

[0058] According to one embodiment of the present invention, the thickener may be included in the slurry in an amount of 1 weight% or more and 30 weight% or less. Specifically, the thickener may be included in the slurry in an amount of 4 weight% or more and 25 weight% or less, more specifically in an amount of 5 weight% or more and 20 weight% or less. When the content of the thickener is within the above range, internal hollows and cavities in the shell portion can be easily formed. When the content of the thickener falls outside the above range, fragments that do not maintain the shape of the particles may be formed, or solid particles with a filled interior may be formed.

[0059] According to one embodiment of the present invention, the thickening agent may comprise at least one selected from the group consisting of carboxymethylcellulose, ethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, polyvinyl alcohol, polyvinyl acetate, polyethylene oxide, polyvinyl ether, polyacrylic acid, polycarboxylic acid, polyisocyanate, carbomer, guar gum, and xanthan gum. More specifically, the thickening agent may be polyvinyl alcohol.

[0060] According to one embodiment of the present invention, the viscosity of the slurry may be 10 cPs to 300 cPs. The viscosity of the slurry may be 10 cPs to 250 cPs, 10 cPs to 200 cPs, 10 cPs to 150 cPs, or 10 cPs to 100 cPs. When the viscosity of the slurry is controlled within the above range, the composite formed by the above manufacturing method may predominantly form hollow spherical particles having cavities. The viscosity may be measured by a spindle rotation method using a rotary viscometer under conditions of room temperature (25 ℃) and 20 rpm. In addition, the solid content in the slurry may be 5 volume% to 40 volume%, 10 volume% to 30 volume%, 15 volume% to 30 volume%, 15 volume% to 25 volume%, or 15 volume% to 20 volume%.

[0061] Spray drying stage

[0062] The spray drying method in the above spray drying step may involve introducing the slurry into a spray dryer to form granular particles. Depending on the atomizing method, the spray drying method may be classified into a rotating type using the rotation of a disk or a nozzle type using an air nozzle. According to one embodiment of the present invention, the spray drying method may utilize a rotating spray drying method. In this case, the slurry is conveyed to a rotating disk, and droplets may be formed by the centrifugal force resulting from the high rotational speed of the disk. The droplets sprayed by the rotating spray drying method may be advantageous for forming hollow granules with cavities, as their surfaces are dried at a rapid speed by the high-temperature hot air inside the chamber.

[0063] According to one embodiment of the present invention, the spray drying step may be performed under rotational speeds of 5,000 rpm to 15,000 rpm and temperature conditions of 110 ℃ to 300 ℃. Specifically, the rotational speed of the spray drying step may be 5,500 rpm to 15,000 rpm, 6,000 rpm to 14,000 rpm, 6,000 rpm to 13,000 rpm, 6,000 rpm to 12,000 rpm, or 6,500 rpm to 11,000 rpm. Additionally, the temperature range in the spray drying step may be 130 ℃ to 280 ℃, 150 ℃ to 270 ℃, 180 ℃ to 260 ℃, or 200 ℃ to 250 ℃. Within the above rotational speed range and temperature range, the formation of granular particles having an internal hollow and a cavity on the surface can be predominantly controlled through spray drying. Specifically, by controlling within the above rotational speed range, the shape of the particles formed through spray drying can be formed into a spherical shape, and the particle size can be controlled to 10 μm to 300 μm. Furthermore, by controlling within the above temperature range, the particles formed through spray drying can maintain a spherical shape, the internal solvent can be discharged to the outside, and a cavity can be formed in the internal hollow and the shell.

[0064] Sintering stage

[0065] The above sintering step may involve heating and crystallizing the granular particles formed through the above spray drying step.

[0066] According to one embodiment of the present invention, the sintering step may be performed within a sintering temperature range of 1,000 ℃ to 1,800 ℃. Specifically, the sintering temperature may be controlled according to the content of the inorganic additive. Depending on the content of the inorganic additive, the sintering temperature may be 1,200 ℃ to 1,800 ℃, 1,200 ℃ to 1,700 ℃, 1,200 ℃ to 1,600 ℃, or 1,250 ℃ to 1,550 ℃. The sintering temperature is significantly lower than the sintering temperature of general magnesium oxide, and since sintering is possible even at a lower sintering temperature due to increased diffusivity depending on the type and content of the additive, there is an advantage of excellent economic efficiency.

[0067] According to one embodiment of the present invention, after the sintering step, a step of separating and recovering hollow magnesium oxide composites having cavities according to particle size may be further included. The separation and recovery step may utilize sieving, gravity classification, or centrifugal classification. Through the separation and recovery step, hollow magnesium oxide composites having cavities of uniform particle size and sintered particles having cavities with controlled cavity sizes according to the purpose can be separated and recovered.

[0068] Another embodiment of the present invention provides an organic-inorganic composite in which particles composed of a hollow magnesium oxide composite having the cavity are dispersed within a polymer matrix.

[0069] According to one embodiment of the present invention, the organic-inorganic composite may be one in which the internal hollow of the hollow magnesium oxide composite having the cavity is filled with the polymer matrix.

[0070] According to one embodiment of the present invention, the polymer matrix may be formed from at least one resin selected from the group consisting of silicone resins, urethane resins, epoxy resins, and thermoplastic resins. The silicone resin, urethane resin, epoxy resin, and thermoplastic resin may be materials for forming a matrix that are generally used in the industry. For example, the thermoplastic resin may include polyolefin resins and polyester resins. In addition, the thermoplastic resin may include at least one of general-purpose plastics such as PE, PP, PMMA, PS, ABS, etc., engineering plastics such as PBT, PC, PPO, POM, Nylon, etc., super engineering plastics such as PPS, PI, PTFE, PEEK, etc., and eco-friendly plastics such as PBAT, PLA, etc.

[0071] According to one embodiment of the present invention, the hollow magnesium oxide composite having the cavity may be used for at least one of a heat transfer material, a heat dissipation material, a wear-resistant material, an insulating material, a flame-retardant material, and a reinforcing material. Specifically, since the hollow magnesium oxide composite having the cavity has excellent thermal conductivity and moisture resistance, it may be applied to a heat dissipation layer, a heat dissipation filler, etc., within a semiconductor device, but is not limited thereto. It may be applied to existing applications of alumina and / or silica, and more broadly, it may be applied without limitation to polymer resin-based heat transfer materials, wear-resistant materials, insulating materials, flame-retardant materials, and reinforcing materials.

[0072] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0073] [Examples 1 to 8]

[0074] Mg(OH)2 powder as a magnesium oxide precursor, Nb2O5 powder and TiO2 powder as inorganic additives as shown in Table 1 below were added to distilled water, and a polycarboxylate ammonium salt-based dispersant, ammonium hydroxide as a dispersion stabilizer, and polyvinyl alcohol (PVA) as a thickener were added and stirred to prepare a mixture. The mixture prepared above was further mixed and ground using a ball mill with ZrO2 beads to prepare a slurry. Then, granulation was performed using a spray drying method under the atomizer rotation speed and temperature shown in Table 1 below. Subsequently, the granulated particles were sintered at the temperature shown in Table 1 below to produce sintered particles. The evaluation of the formation of hollow particles with cavities (hollow magnesium oxide composites with cavities) among the prepared sintered particles is shown in Table 1 below.

[0075] Classification Inorganic Additive (Amount added relative to 1 mol of Mg(OH)2 (mol%)) Slurry Components (Content in slurry) Spray Drying Conditions Sintering Temperature (°C) Formation of Hollow Particles with Cavities Cavity Diameter (㎛) Epoxy Filling Presence Dispersant (wt%) Dispersion Stabilizer (wt%) PVA (wt%) Solids (vol%) Viscosity (cPs) Temperature (°C) rpm Example 1 Nb2O5, TiO2 (0.045, 0.15) 2.6 4.4 2 15 10 2 40 10,000 1450 ○ 1~10X Example 2 Nb2O5, TiO2 (0.045, 0.15) 2.6 4.4 3 15 12 2 40 10,000 1450 ○ 2~20X Example 3 Nb2O5, TiO2 (0.045, 0.15)2.64.44151924010,0001450○3~25△Example 4 Nb2O5, TiO2(0.045, 0.15)2.64.45152124010,0001450○3~30○Example 5 Nb2O5, TiO2(0.045, 0.15)2.64.47152924010,0001450○5~30◎Example 6 Nb2O5, TiO2(0.045, 0.15)2.64.410155024010,0001450○5~35◎Example 7 Nb2O5, TiO2(0.045, 0.15)2.64.412156424010,0001450○5~40◎Example 8 Nb2O5, TiO2(0.045, 0.15)2.64.415158124010,0001450○5~40◎Comparative Example 1 Nb2O5, TiO2(0.045, 0.15)---15106923010,0001450X-XComparative Example 2 Nb2O5, TiO2(0.045, 0.15)2.64.4-157.523010,0001450X-XReference Example 1 Nb2O5, TiO2(0.045, 0.15)2.6-0.51526823010,0001450X-X

[0076] - Formation of hollow particles with cavities: ○ indicates the case where hollow particles with cavities are formed and observed in the manufactured sintered particles, and X indicates the case where hollow particles with cavities are not observed among the manufactured sintered particles. When using SEM to confirm the formation of hollow particles with cavities, it may be difficult to distinguish if cavities are formed on the side or opposite side of the particle. Therefore, SEM can be used to confirm the formation of hollow particles with cavities, and furthermore, it can be confirmed through the cross-sectional analysis after epoxy filling described below.

[0077] - Epoxy filling status: To determine whether a polymer material is filled inside hollow particles with cavities, a method was used in which sintered particles were impregnated with epoxy resin (Epofix, Struers) and cured to produce an epoxy-filler composite, which was then polished to observe the cross-section. In this case, ◎ indicates that 80% or more of the manufactured hollow particles with cavities are filled with epoxy resin, ○ indicates that 50% or more but less than 80% of the manufactured hollow particles with cavities are filled with epoxy resin, △ indicates that 20% or more but less than 50% of the manufactured hollow particles with cavities are filled with epoxy resin, and X indicates that less than 20% of the manufactured hollow particles with cavities are filled with epoxy resin.

[0078] Figure 2 shows an example for determining the degree of internal filling of a hollow particle having a cavity when impregnated with epoxy resin.

[0079] - Slurry viscosity: Refers to the viscosity measured for 30 seconds at 20 rpm using a low-viscosity spindle (L2) at room temperature (25 ℃) using a viscometer (ViscoQC 300-L, Anton Paar).

[0080] FIGS. 3 to 10 are SEM images showing sintered particles prepared according to Examples 1 to 8, respectively. Referring to FIGS. 3 to 10, it can be seen that a number of sintered particles densely form a shell portion with magnesium oxide crystal grains, and furthermore, a cavity connecting the shell portion to the hollow is formed. In particular, referring to FIGS. 5b, 6b, and 7b, it can be seen that the cavity is surrounded by magnesium oxide crystal grains forming the shell portion. Additionally, it can be seen that as the content of the thickener in the slurry increases, the diameter of the cavity increases and the frequency of forming hollow particles with cavities increases; however, it can be seen that if the amount becomes excessive, the particle tends to fail to maintain its shape and fragment.

[0081] Figures 11a and 11b are SEM images showing a cross-section of a sintered particle prepared according to Comparative Example 1, respectively. Specifically, Figure 11b shows the cross-section of a sintered particle after impregnating it with epoxy resin to check whether an internal hollow was formed in the sintered particle according to Comparative Example 1, and it was confirmed that no internal hollow was formed, and furthermore, no cavity was formed.

[0082] In addition, FIGS. 12 and FIGS. 13 are SEM images showing sintered particles prepared according to Comparative Example 2 and Reference Example 1, respectively. Specifically, as can be seen from the SEM images of the sintered particles according to Comparative Example 2 and Reference Example 1, no cavity was observed in the shell portion, and it was confirmed that the particles were solid particles with no hollows observed even when observing their cross-section.

[0083] Through the results according to the examples, comparative examples, and reference examples, it can be confirmed that by applying a dispersant and a dispersion stabilizer together when forming a slurry as in the present invention and controlling the content of a thickener, sintered particles having hollows with cavity sizes controlled according to the purpose can be obtained.

[0084] In addition, to evaluate the hygroscopicity of the manufactured sintered particles, a hygroscopicity test was performed on the sintered particles manufactured according to Example 5, and the degree of change was analyzed through XRD analysis.

[0085] Figure 14 shows the XRD analysis results before and after a 72-hour test at 85°C and 85%RH of the sintered particles prepared according to Example 5. As shown in Figure 14, it was confirmed that after the moisture resistance test, no magnesium hydroxide phase was detected in the sintered particles due to moisture absorption, and the magnesium oxide phase remained well maintained, just as it was before the test.

Claims

1. A core part having a hollow space; and A shell portion comprising magnesium oxide crystal grains and a metal element different from magnesium, and having at least one cavity communicating with the hollow; Hollow magnesium oxide composite having a cavity.

2. In Claim 1, A hollow magnesium oxide composite having a cavity, wherein the metal element comprises at least one selected from the group consisting of Ti, Nb, Zr, Ga, B, Fe, Sn, Mn, Si, V, Ta, Sb, Y, Eu, Er, Al, and Yb.

3. In Claim 1, A hollow magnesium oxide composite having a cavity, wherein the metal element is substituted at the position of the magnesium element of the magnesium oxide crystal grain.

4. In Claim 1, A hollow magnesium oxide composite having a cavity, wherein the metal element is provided in the form of an oxide on the surface of the magnesium oxide crystal grains.

5. In Claim 1, A hollow magnesium oxide composite having a cavity, wherein the content of the metal element is 0.02 at.% or more and 6 at.% or less with respect to the magnesium element.

6. In Claim 1, A hollow magnesium oxide composite having a cavity, wherein the cavity is surrounded by magnesium oxide crystal grains of the shell portion.

7. In Claim 1, A hollow magnesium oxide composite having a cavity, wherein the diameter of the cavity is 0.01 to 0.7 times the particle diameter of the composite.

8. In Claim 1, A hollow magnesium oxide composite having a cavity, wherein the particle size of the hollow magnesium oxide composite having the cavity is 10 μm to 300 μm.

9. In Claim 1, A hollow magnesium oxide composite having a cavity, wherein the above-mentioned hollow is composed of 1 to 20 spherical pores.

10. A slurry preparation step of forming a slurry by mixing a magnesium oxide precursor comprising at least one of Mg(OH)2 powder and MgO powder, an inorganic additive, a thickener, a dispersant, and water; A spray drying step of preparing the above slurry into granular powder using a spray drying method; and A sintering step comprising crystallizing the above granular powder by sintering treatment; Method for manufacturing a hollow magnesium oxide composite having a cavity.

11. In Claim 10, A method for manufacturing a hollow magnesium oxide composite having a cavity, wherein the viscosity of the slurry is 10 cPs to 300 cPs.

12. In Claim 10, A method for manufacturing a hollow magnesium oxide composite having a cavity, wherein the above-mentioned inorganic additive is selected from the group consisting of oxides, hydroxides, or carbonates comprising at least one selected from the group consisting of Ti, Nb, Zr, Ga, B, Fe, Sn, Mn, Si, V, Ta, Sb, Y, Eu, Er, Al, and Yb.

13. In claim 10, A method for manufacturing a hollow magnesium oxide composite having a cavity, wherein the above-mentioned thickener comprises at least one selected from the group consisting of carboxymethylcellulose, ethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, polyvinyl alcohol, polyvinyl acetate, polyethylene oxide, polyvinyl ether, polyacrylic acid, polycarboxylic acid, polyisocyanate, carbomer, guar gum, and xanthan gum.

14. In Claim 10, A method for manufacturing a hollow magnesium oxide composite having a cavity, wherein the above-mentioned thickener is included in the above-mentioned slurry in an amount of 1% by weight or more and 30% by weight or less.

15. In Claim 10, A method for manufacturing a hollow magnesium oxide composite having a cavity, wherein the above spray drying step is performed under rotational speed of 5,000 rpm to 15,000 rpm and temperature conditions of 110 ℃ to 300 ℃.

16. In Claim 10, A method for manufacturing a hollow magnesium oxide composite having a cavity, wherein the above-mentioned slurry manufacturing step further includes a dispersion stabilizer.

17. In Claim 10, A method for manufacturing a hollow magnesium oxide composite having a cavity, wherein the above sintering step is performed within a sintering temperature range of 1,000 ℃ to 1,800 ℃.

18. An organic-inorganic composite comprising particles composed of a hollow magnesium oxide composite having a cavity according to Claim 1, dispersed within a polymer matrix.

19. In Claim 18, An organic-inorganic composite having the above cavity, wherein the internal hollow of the hollow magnesium oxide composite having the above cavity is filled with the above polymer matrix.

Images